22 LECTURE II. 



leaf-forming shoots spring not laterally from roots, but direct from their growing 

 points, of which, however, but few examples are known as yet. 



This fact has been longest known in Neotiia Nidus Avis, an orchid of our 

 woods, the leaves of which are not green ; of the numerous and short, stout roots 

 of its subterranean stem, some produce leaf-buds from their growing points, the 

 root-cap becomes torn and pushed aside, and the root apex forthwith transformed 

 into a shoot. Goebel has described the same fact in the root of an Aroid 

 {Anthuriiun longi/oIium)\n our gardens ^ and apparently the fact is just the same in a 

 fern cultivated here {Platycerium Willitigkii). In this category w-e may also place 

 the transformation of the roots of Selaginella into leaf-shoots ^ In these plants, 

 belonging to the class Lycopodiaceae among the Vascular Cryptogams, the leaf- 

 shoots become branched in a forked manner, and at the points of branching 

 appear fihform structures, also dichotomously branched, which in many species 

 are at once possessed of the properties of roots, in other species, however, are 

 somewhat different from common roots, and are then called Rhizophores, because 

 they assume the form of ordinary roots only on penetrating the soil. In some 

 species of Selaginella {S. Martensii, inocgicalifolia, hrviga/a), these rhizophores may 

 acquire the form of leafy shoots. 



' Compare Goebel, Bot. Zeit. 1878, p. 645. 



- Compare Pfeffer, in Hanstein's botanischen Abhandlungen, Bonn, I. p. 67, and Sachs, Lehr- 

 buch, IV. Aufl. pp. 171, 470. 



